Life Cycle Assessment – Sonic / INDEX.01

The launch of the INDEX.01 was a huge step forward for Salomon in terms of sustainability, allowing us to explore a different way of designing, producing and disposing of a pair of shoes. Since it launched in 2021, the first recyclable running shoe was tested, worn, used and sent back to be recycled into ski boots, as it was designed to be.


“Shoes are a very complex product to recycle because they mix so many materials,” said Olivier Mouzin, Manager of Salomon’s Footwear Sustainability Program

The INDEX.01 was designed with a “Cradle to Cradle” state of mind, where Salomon is controlling every step of the lifecycle of the shoe, from selecting the base materials to the production process to handling its transportation and ensuring that it is recycled at the end of life. The INDEX.01 has a minimalist design: no crazy shapes or extra pieces, just the essentials. This is what allows the shoe to be recycled and used in a new product, since it is easier to split the different parts of the shoe.

“Shoes are a very complex product to recycle because they generally mix so many materials: leather, EVA, rubber, TPU, polyester, polyamide,” explains Olivier Mouzin, Manager of Salomon’s Footwear Sustainability Program. “And because there isn’t really a way to separate all those materials at the end of the shoe’s life, the shoes often end up in a landfill or burned.”

The INDEX.01 was constructed with two main materials that could be separated and recycled, while making sure that these materials would pass our standards for everyday road-running in terms of fit, performance and durability. For the bottom unit, that means finding the perfect amount of shock absorption and rebound, which the footwear team found in a nitrogen-infused, TPU-based foam called INFINIRIDE. The upper of the shoe was made with virgin and recycled polyester. The thread used to stitch the two parts together is also polyester, and water-based glue connects both parts. All that is left to do once the shoe has been used and sent back is to grind down the separate parts and combine them either with virgin TPU or virgin polyester to make alpine skis boots (in Europe) or polyester fabrics for other types of products.


Let’s talk numbers. What does the INDEX.01 bring to the table? What is the environmental impact of the shoe when you take into consideration the few materials used to make it and the fact that it is recycled, instead of incinerated or put in a landfill? To assess the impact of the shoe, we need to know what the impact of a “regular” running shoe is. Olivier Mouzin, along with the Salomon footwear team, assessed the impact of the Sonic 3 road-running shoe.

“The goal of a lifecycle analysis is to identify the pieces or processes with the biggest environmental impact during the life-cycle of the product, in order to work on reducing it”, Mouzin explains.

Assessing the life cycle of a shoe means compiling and evaluating the inputs, outputs and potential environmental impacts of a shoe throughout its lifecycle. The goal is to provide scientific and measured data for each step of its lifecycle: raw materials selection, the production process, the packaging, the shipping, the usage of the product and the end of life. This allows us to clearly tell the impact of each step in terms of carbon emissions, use of natural resources, water eutrophication from nitrates (caused by the cooling of machines and colorization) and water acidification, among other aspects (17 in total). Thanks to this analysis, we can tell how the INDEX.01 compares to regular road-running shoes.

“A lifecycle analysis identifies the biggest environmental impact during the life-cycle of the product, in order to work on reducing it,” said Olivier Mouzin, Manager of Salomon’s Footwear Sustainability Program

The way the INDEX.01 is made and the fact that it can be recycled reduces by 44 percent the amount of CO2 compared to a traditional shoe, which is 4.9kg of CO2 Eq less for every pair. The emissions from the lifecycle of the Sonic 3 are 11,2kg of CO2 Eq; the INDEX.01 emits 6,3kg of CO2 Eq. Water eutrophication is reduced by 70 percent, and water acidification is reduced by 35 percent.

“The INDEX.01 is a great start for sustainable footwear: we can test out this new, simple design and it’s performance on the road, and test out the collecting and recycling process. As the lifecycle analysis shows, the impact of the shoe is lessened by 44 percent, which validates our work and encourages us to develop more footwear products following this circular economy concepts,” Olivier Mouzin explains.

Here is a more detailed view of what steps of the lifecycle if the shoe change from the Sonic 3 to the INDEX.01, produced in the same factory.

Raw materials: +22 percent of emissions. The TPU used for the INDEX.01 is more impactful than the usual EVA and slightly heavier (+70g).
Shoe production: -45 percent of emissions. This is where a big chunk of the emissions is reduced, thanks to using fewer materials, a minimalist design with a classical sewing process, and a new injection process for the midsole and the outsole.
Packaging: -8 percent of emissions. This is due to the removal of the stuffing paper from the boxes. All Salomon boxes for shoes are FSC certified.
Distribution: +15 percent of emissions. The INDEX.01 being 70g heavier makes it more impactful to ship the shoe, including when it is sent back for recycling.
Recycling: -2.1Kg of CO2 Eq. The recycling process eliminates all the emissions from burning or putting the shoe in a landfill, which is what usually happens at the end of the life of a shoe. Here, the TPU from the ground down shoe is being reused in our new MTN touring ski boots. Technically, half of the emissions reduction can be allocated to the INDEX.01, and the other half goes to the MTN ski boot.


As you can tell from the graph above, recycling the INDEX.01 is what greatly helps reduce its impact. Meaning that if the shoe is not recycled, it loses its purpose. So, if you own a pair of INDEX.01 shoes and you have run in them until your pinkie toe sticks out: PLEASE RECYCLE THEM.

You can do so by clicking here, where you can print a shipping label to send your shoes to your closest collection center. If you buy your INDEX.01 from April 19th, simply scan the QR code on the tongue of the shoe. To minimize transportation impact, the shoes will be received at collection centers in Europe, North America and the Asia/Pacific regions. There, they will be washed and disassembled before each material is sent for recycling locally.

The INDEX.01 is part of Salomon’s Play-Minded program, which aims at reducing our carbon emissions by 30 percent by 2030 and investing 1 percent of our annual revenue into educating people who play in the mountains. Salomon has also pledged to design 100 percent of new Salomon products to one or several of our circular economy principles, just like the INDEX.01:

Product lifecycle: assess and estimate our core products’ sustainability impacts, and seek low impact alternatives for design (less components), development and production process
Resource efficiency: Using lightweight and recycled or bio-based content
Durability & repair: Quality design and durable products, advising on care and providing repair services
End of use: How to return products (recycling or product take-back), closing the loop by being able to remanufacture or upgrade products and by designing products which are recyclable.
Look out for the INDEX Break, a sandal releasing this Spring 2022, which uses the same materials as the INDEX.01 in order to be worn, separated, then fully recycled. The MTN ski touring range, releasing Winter 2022, will use the ground-down TPU from the INDEX. 01.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button